Position Match function implementations

Implementation of get and set functions for position-compare attribute
Implementation of mode change to position-compare
Initialization of position compare
Disable/Enable unit timer

Attempt to disable and enable unit timer when switching between relative
and absolute modes.  This is to disable period interrupts when not used
for velocity calculations.
Begin add position-match to c++ API

Updated typedef for eQep modes
Added function prototypes to eQep class